Field
Implementations of the present disclosure generally relate to methods and apparatuses for removing contaminants and oxides from a substrate surface.
Description of the Related Art
Integrated circuits are formed in and on silicon and other semiconductor substrates. In the case of single crystal silicon, substrates are made by growing an ingot from a bath of molten silicon, and then sawing the solidified ingot into multiple wafers. An epitaxial silicon layer may then be formed on the monocrystalline silicon wafer to form a defect free silicon layer that may be doped or undoped. Semiconductor devices, such as transistors, are manufactured from the epitaxial silicon layer. The electrical properties of the formed epitaxial silicon layer will generally be better than the properties of the monocrystalline silicon substrate.
Surfaces of the monocrystalline silicon and the epitaxial silicon layer are susceptible to contamination when exposed to ambient conditions at a typical substrate fabrication facility. For example, a native oxide layer may form on the monocrystalline silicon surface prior to deposition of the epitaxial layer. If the monocrystalline silicon were doped with germanium, germanium will react with the silicon and form silicon-germanium alloy as well as native oxides of germanium and/or silicon-germanium alloy on the surface of the germanium-doped silicon. Additionally, hydrocarbons present in the ambient environment may react with germanium oxides and form germanium carbons on the surface of the germanium-doped silicon. The presence of native oxides of germanium, silicon-germanium alloy, or carbon residues on the germanium-doped silicon surface not only negatively affects the quality of an epitaxial layer subsequently formed on the germanium-doped silicon surface, but is also difficult to remove during cleaning of the substrate.
Therefore, there is a need for methods for cleaning a substrate surface, especially for cleaning a substrate surface prior to performing an epitaxial deposition process.